George Osborne, the Chancellor, said that “it is right that we take our time and get the right decision.”

When pressed on when the Government expected to make a decision, Mrs Soubry said evidence was not emerging from Australia as quickly as ministers had hoped.

She told the Commons: "I have absolutely no problem whatsoever with waiting and seeing how the introduction of this legislation has happened in Australia.

"If you have got a good effectively an experiment up and running that will produce evidence, what could be more sensible for government to do?

"As to the length of time, I can't answer that question, because we have to wait and see the evidence as it emerges.

"One of the things that struck me and quite surprised me, I thought we might be able to see some sort of change quite quickly in Australia and we haven't seen that at the moment.

"So I'm afraid it's how long is a piece of string?

"We have to wait and see how the evidence is emerging."

Asked if the Prime Minister had discussed tobacco packaging Mr Crosby, a Downing Street spokesman said: “The Prime Minister has never been lobbied by Lynton Crosby on cigarette packaging. Lynton Crosby has had no involvement in the decision.”